package com.chrisbanes.photoview;

import android.content.Context;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.VelocityTracker;
import android.view.ViewConfiguration;

class PhotoGestureDetector {

    private static final int INVALID_POINTER_ID = -1;

    private final ScaleGestureDetector mScaleGestureDetector;

    private OnGestureListener mGestureListener;

    private float mLastTouchX;

    private float mLastTouchY;

    private final float mTouchSlop;

    private final float mMinimumVelocity;

    private VelocityTracker mVelocityTracker;

    private boolean mIsDragging;

    private int mActivePointerId = INVALID_POINTER_ID;

    private int mActivePointerIndex = 0;

    public interface OnGestureListener {

        void onDrag(float dx, float dy);

        void onFling(float startX, float startY, float velocityX, float velocityY);

        void onScaling(float scaleFactor, float focusX, float focusY);

        void onScaleEnd(float focusX, float focusY);
    }

    public PhotoGestureDetector(Context context, OnGestureListener onGestureListener) {

        mGestureListener = onGestureListener;
        final ViewConfiguration configuration = ViewConfiguration.get(context);
        mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
        mTouchSlop = configuration.getScaledTouchSlop();

        ScaleGestureDetector.OnScaleGestureListener mScaleListener = new ScaleGestureDetector
                .OnScaleGestureListener() {

            @Override
            public boolean onScale(ScaleGestureDetector detector) {

                float scaleFactor = detector.getScaleFactor();

                if (Float.isNaN(scaleFactor) || Float.isInfinite(scaleFactor)) {
                    return false;
                }

                mGestureListener.onScaling(scaleFactor, detector.getFocusX(), detector.getFocusY());
                return true;
            }

            @Override
            public boolean onScaleBegin(ScaleGestureDetector detector) {

                return true;
            }

            @Override
            public void onScaleEnd(ScaleGestureDetector detector) {
                mGestureListener.onScaleEnd(detector.getFocusX(), detector.getFocusY());
            }
        };
        mScaleGestureDetector = new ScaleGestureDetector(context, mScaleListener);
    }

    public boolean isScaling() {

        return mScaleGestureDetector.isInProgress();
    }

    public boolean isDragging() {

        return mScaleGestureDetector.isInProgress();
    }

    public boolean onTouchEvent(MotionEvent ev) {

        try {
            mScaleGestureDetector.onTouchEvent(ev);
            return processTouchEvent(ev);
        } catch (IllegalArgumentException e) {
            // Fix for support lib bug, happening when onDestroy is called
            return true;
        }
    }

    private boolean processTouchEvent(MotionEvent ev) {
        switch (ev.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN: {
                mActivePointerId = ev.getPointerId(0);
                mVelocityTracker = VelocityTracker.obtain();
                if (null != mVelocityTracker) {
                    mVelocityTracker.addMovement(ev);
                }

                mLastTouchX = ev.getX(mActivePointerIndex);
                mLastTouchY = ev.getY(mActivePointerIndex);
                mIsDragging = false;
                break;
            }

            case MotionEvent.ACTION_MOVE: {
                final float x = ev.getX(mActivePointerIndex);
                final float y = ev.getY(mActivePointerIndex);
                final float dx = x - mLastTouchX, dy = y - mLastTouchY;

                if (!mIsDragging) {
                    // Use Pythagoras to see if drag length is larger than touch slop
                    mIsDragging = Math.sqrt((dx * dx) + (dy * dy)) >= mTouchSlop;
                }

                if (mIsDragging) {
                    mGestureListener.onDrag(dx, dy);
                    mLastTouchX = x;
                    mLastTouchY = y;

                    if (null != mVelocityTracker) {
                        mVelocityTracker.addMovement(ev);
                    }
                }
                break;
            }

            case MotionEvent.ACTION_CANCEL: {
                mActivePointerId = INVALID_POINTER_ID;
                // Recycle Velocity Tracker
                if (null != mVelocityTracker) {
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }
                break;
            }

            case MotionEvent.ACTION_UP: {
                mActivePointerId = INVALID_POINTER_ID;
                if (mIsDragging) {
                    if (null != mVelocityTracker) {
                        mLastTouchX = ev.getX();
                        mLastTouchY = ev.getY();

                        // Compute velocity within the last 1000ms
                        mVelocityTracker.addMovement(ev);
                        mVelocityTracker.computeCurrentVelocity(1000);

                        final float vX = mVelocityTracker.getXVelocity(), vY = mVelocityTracker.getYVelocity();

                        // If the velocity is greater than minVelocity, call
                        // listener
                        if (Math.max(Math.abs(vX), Math.abs(vY)) >= mMinimumVelocity) {
                            mGestureListener.onFling(mLastTouchX, mLastTouchY, -vX, -vY);
                        }
                    }
                }

                // Recycle Velocity Tracker
                if (null != mVelocityTracker) {
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }
                break;
            }

            case MotionEvent.ACTION_POINTER_UP:
                // Ignore deprecation, ACTION_POINTER_ID_MASK and
                // ACTION_POINTER_ID_SHIFT has same value and are deprecated
                // You can have either deprecation or lint target api warning
                final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent
                        .ACTION_POINTER_INDEX_SHIFT;
                final int pointerId = ev.getPointerId(pointerIndex);
                if (pointerId == mActivePointerId) {
                    // This was our active pointer going up. Choose a new
                    // active pointer and adjust accordingly.
                    final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                    mActivePointerId = ev.getPointerId(newPointerIndex);
                    mLastTouchX = ev.getX(newPointerIndex);
                    mLastTouchY = ev.getY(newPointerIndex);
                }
                break;
        }
        mActivePointerIndex = ev.findPointerIndex(
                mActivePointerId != INVALID_POINTER_ID ? mActivePointerId : 0);

        return true;
    }
}
